Method for manufacturing optical device structures

ABSTRACT

Embodiments described herein provide for methods of forming optical device structures. The methods utilize rotation of a substrate, to have the optical device structures formed thereon, and tunability of etch rates of a patterned resist disposed over the substrate and one of a device layer or the substrate to form the optical device structures without multiple lithographic patterning steps and angled etch steps.

BACKGROUND Field

Embodiments of the present invention generally relate to optical devicesfor augmented, virtual, and mixed reality. More specifically,embodiments described herein provide for forming blazed optical devicestructures.

Description of the Related Art

Virtual reality is generally considered to be a computer generatedsimulated environment in which a user has an apparent physical presence.A virtual reality experience can be generated in 3D and viewed with ahead-mounted display (HMD), such as glasses or other wearable displaydevices that have near-eye display panels as lenses to display a virtualreality environment that replaces an actual environment.

Augmented reality, however, enables an experience in which a user canstill see through the display lenses of the glasses or other HMD deviceto view the surrounding environment, yet also see images of virtualobjects that are generated for display and appear as part of theenvironment. Augmented reality can include any type of input, such asaudio and haptic inputs, as well as virtual images, graphics, and videothat enhances or augments the environment that the user experiences. Asan emerging technology, there are many challenges and design constraintswith augmented reality.

One such challenge is displaying a virtual image overlaid on an ambientenvironment. Optical devices including waveguide combiners, such asaugmented reality waveguide combiners, and flat optical devices, such asmetasurfaces, are used to assist in overlaying images. Generated lightis propagated through an optical device until the light exits theoptical device and is overlaid on the ambient environment. Opticaldevices may require structures having blazed angles relative to thesurface of the optical device substrate. Conventionally, fabricatingblazed optical device structures using one or more angled etch toolsrequires multiple lithographic patterning steps and angled etch steps.The multiple lithographic patterning steps and angled etch stepsincrease fabrication time and increase cost.

Accordingly, what is needed in the art are improved methods of formingoptical devices including blazed optical device structures with angledetch tools.

SUMMARY

In one embodiment, a method is provided. The method includes positioninga substrate at a first rotation angle ϕ₁ in the path of a beam. The beamis configured to be projected to a surface of the substrate at a beamangle ϑ relative to a surface normal of the substrate. A patternedresist is formed over the substrate where the patterned resist includestwo or more resist structures and one or more gaps. Each of the resiststructures has a width and each of the gaps is defined by adjacentresist structures and has a linewidth defined by the adjacent resiststructures. The method includes etching the substrate positioned at thefirst rotation angle ϕ₁ with the beam and rotating the substrate to asecond rotation angle ϕ₂ and etching sidewalls of the resist structuresoriented toward the beam such that the width of the resist structuresdecreases and the linewidth of the gaps increases. The method furtherincludes rotating the substrate to the first rotation angle ϕ₁ andetching the substrate at the first rotation angle ϕ₁ with the beam andforming two or more optical device structures in the substrate. Theforming the optical device structures includes repeating the rotatingthe substrate to the second rotation angle ϕ₂ and the etching sidewallsof the resist structures with the beam and the rotating the substrate tothe first rotation angle ϕ₂ and the etching the substrate with the beamuntil the resist structures are removed or the linewidth of the gaps hasa predetermined linewidth.

In another embodiment, a method is provided. The method includespositioning a substrate at a first rotation angle ϕ₁ in the path of abeam. The beam is configured to be projected to a surface of thesubstrate at a beam angle ϑ relative to a surface normal of thesubstrate. A device layer is formed over the substrate and a patternedresist is formed on the device layer. The patterned resist includes twoor more resist structures and one or more gaps. Each of the resiststructures has a width and each of the gaps is defined by adjacentresist structures and has a linewidth defined by the adjacent resiststructures. The method includes etching the device layer with thesubstrate positioned at the first rotation angle ϕ₁ with the beam androtating the substrate to a second rotation angle ϕ₂ and etchingsidewalls of the resist structures oriented toward the beam such thatthe width of the resist structures decreases and the linewidth of thegaps increases. The method further includes rotating the substrate tothe first rotation angle ϕ₁ and etching the device layer at the firstrotation angle ϕ₁ with the beam and forming two or more optical devicestructures in the device layer. The forming the optical devicestructures includes repeating the rotating the substrate to the secondrotation angle ϕ₂ and the etching sidewalls of the resist structureswith the beam and the rotating the substrate to the first rotation angleϕ₂ and the etching the device layer with the beam until the resiststructures are removed or the linewidth of the gaps has a predeterminedlinewidth.

In yet another embodiment, a method is provided. The method includespositioning a substrate at a first rotation angle ϕ₁ in the path of abeam. The beam is configured to be projected to a surface of thesubstrate at a beam angle ϑ relative to a surface normal of thesubstrate. A patterned resist is formed over the substrate where thepatterned resist includes two or more resist structures and one or moregaps. Each of the resist structures has a width and each of the gaps isdefined by adjacent resist structures and has a linewidth defined by theadjacent resist structures. The substrate is etched by the beamgenerated by a substrate etch chemistry and the resist structures areetched by the beam generated by a resist etch chemistry different thanthe substrate etch chemistry. The method further includes etching thesubstrate positioned at the first rotation angle ϕ₁ with the beamgenerated by the substrate etch chemistry and rotating the substrate toa second rotation angle ϕ₂ and etching sidewalls of the resiststructures with the beam at the beam angle ϑ. The beam generated by theresist etch chemistry etches sidewalls of resist structures orientedtoward the beam such that the width of the resist structures decreasesand the linewidth of the gaps increases. The method further includesrotating the substrate to the first rotation angle ϕ₁ and etching thesubstrate at the first rotation angle ϕ₁ with the beam generated by thesubstrate etch chemistry and forming two or more optical devicestructures in the substrate. The forming the optical device structurescomprises repeating the rotating the substrate to the second rotationangle ϕ₂ and the etching sidewalls of the resist structures with thebeam generated by the resist etch chemistry and rotating the substrateto the first rotation angle ϕ₁ and the etching the substrate with thebeam generated by the substrate etch chemistry until the resiststructures are removed or the linewidth of the gaps has a predeterminedlinewidth.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, and may admit to other equally effective embodiments.

FIG. 1A is a perspective, frontal view of an optical device according toembodiments described herein.

FIG. 1B and FIG. 1C are schematic, cross-sectional views of a pluralityof device structures according to embodiments described herein.

FIG. 2 is a schematic, side view of an angled etch system according toembodiments described herein.

FIG. 3 is a schematic cross-sectional view of angled etch systemaccording to embodiments described herein.

FIG. 4 is a flow diagram of a method for forming a plurality of blazeddevice structures of an optical device structure according toembodiments described herein.

FIGS. 5A-5E are schematic, cross sectional views of a portion of asubstrate during a method for forming a plurality of blazed devicestructures according to embodiments described herein.

FIGS. 5F-5J are schematic, top views of a portion of a substrate duringa method for forming a plurality of blazed device structures accordingto embodiments described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments of the present invention generally relate to optical devicesfor augmented, virtual, and mixed reality. More specifically,embodiments described herein provide for methods of forming opticaldevice structures. The methods utilize rotation of a substrate, to havethe optical device structures formed thereon, and tunability of etchrates of a patterned resist disposed over the substrate and one of adevice layer or the substrate to form the optical device structureswithout multiple lithographic patterning steps and angled etch steps.

In one embodiment, the method includes positioning a substrate at afirst rotation angle ϕ₁ in a path of a beam, the beam configured to beprojected to a surface of the substrate at a beam angle ϑ relative to asurface normal of the substrate. The substrate has a patterned resistformed thereover. The patterned resist includes two or more resiststructures. Each of the resist structures has a width and one or moregaps. Each of the gaps is defined by adjacent resist structures andhaving a linewidth defined by the adjacent resist structures. Thesubstrate positioned at the first rotation angle ϕ₁ is etched with thebeam. The substrate is rotated to a second rotation angle ϕ₂ andsidewalls of the resist structures are etched with the beam at the beamangle ϑ such that the width of the resist structures decreases and thelinewidth of the gaps increases. The substrate is rotated to the firstrotation angle ϕ₁ and the substrate is etched at the first rotationangle ϕ₁ with the beam. Two or more optical device structures are formedin the substrate. The forming the optical device structures includesrepeating the rotating the substrate to the second rotation angle ϕ₂ andthe etching sidewalls of the resist structures with the beam, and therotating the substrate to the first rotation angle ϕ₁ and the etchingthe substrate with the beam until the resist structures are removed orthe linewidth of the gaps has a predetermined linewidth.

FIG. 1A illustrates a perspective, frontal view of an optical device100. It is to be understood that the optical device 100 described belowis an exemplary optical device. In one embodiment, which can be combinedwith other embodiments described herein, the optical device 100 is awaveguide combiner, such as an augmented reality waveguide combiner. Inanother embodiment, which can be combined with other embodimentsdescribed herein, the optical device 100 is a flat optical device, suchas a metasurface. The optical device 100 includes a plurality of devicestructures 102 disposed in (as shown in FIG. 1B) or on (as shown in FIG.1C) a substrate 101. As shown in FIG. 1C, the device structures 102 areformed in a device layer 114 formed on the substrate 101. The devicestructures 102 may be nanostructures having sub-micron dimensions, e.g.,nano-sized dimensions, such as critical dimensions less than 1 μm. Inone embodiment, which can be combined with other embodiments describedherein, regions of the device structures 102 correspond to one or moregratings 104, such as a first grating 104 a, a second grating 104 b, anda third grating 104 c. In one embodiment, which can be combined withother embodiments described herein, the optical device 100 is awaveguide combiner that includes at least the first grating 104 acorresponding to an input coupling grating and the third grating 104 ccorresponding to an output coupling grating. The waveguide combineraccording to the embodiment, which can be combined with otherembodiments described herein, may include the second grating 104 bcorresponding to an intermediate grating.

FIG. 1B and FIG. 1C are schematic, cross-sectional view of a pluralityof device structures 102. In one embodiment, which can be combined withother embodiments described herein, the device structures 102 are blazeddevice structures 106 of a flat optical device, such as a metasurface.The method 400 described herein forms the blazed devices structures 106.In another embodiment, which can be combined with other embodimentsdescribed herein, the device structures 102 are blazed device structures106 of a waveguide combiner, such as an augmented reality waveguidecombiner. The waveguide combiner according to the embodiment, which canbe combined with other embodiments described herein, may include blazeddevices structures 106 in at least one of the gratings 104. Each of theblazed device structures 106 includes a blazed surface 108, a sidewall112, a depth h, and a linewidth d. The blazed surface 108 has aplurality of steps 110. In one embodiment, which can be combined withother embodiments described herein, the blazed surface 108 includes atleast 16 steps 110, such as greater than 32 steps 110, for example 64steps 110. The blazed surface 108 has a blaze angle γ. The blaze angle γis the angle between the blazed surface 108 and the surface parallel pof the substrate 101 and the angle between the surface normal of thesubstrate 101 and facet normal f of the blazed surface 108. The depth hcorresponds to the height of the sidewall 112 and the linewidth dcorresponds to the distances between sidewalls 112 of adjacent blazeddevice structures 106.

In one embodiment, which can be combined with other embodimentsdescribed herein, the blaze angle γ of two or more blazed devicesstructures 106 are different. In another embodiment, which can becombined with other embodiments described herein, the blaze angle γ oftwo or more blazed devices structures 106 are the same. In oneembodiment, which can be combined with other embodiments describedherein, the depth h of two or more blazed devices structures 106 aredifferent. In another embodiment, which can be combined with otherembodiments described herein, the depth h of two or more blazed devicesstructures 106 are the same. In one embodiment, which can be combinedwith other embodiments described herein, the linewidth d of two or moreblazed devices structures 106 are different. In another embodiment,which can be combined with other embodiments described herein, thelinewidths d of one or more blazed devices structures 106 are the same.

The substrate 101 may also be selected to transmit a suitable amount oflight of a desired wavelength or wavelength range, such as one or morewavelengths from about 100 to about 3000 nanometers. Without limitation,in some embodiments, the substrate 101 is configured such that thesubstrate 101 transmits greater than or equal to about 50% to about 100%of an IR to UV region of the light spectrum. The substrate 101 may beformed from any suitable material, provided that the substrate 101 canadequately transmit light in a desired wavelength or wavelength rangeand can serve as an adequate support for the blazed devices structures106 (when the blazed devices structures 106 are formed in the devicelayer 114) described herein. Substrate selection may include substratesof any suitable material, including, but not limited to, amorphousdielectrics, non-amorphous dielectrics, crystalline dielectrics, siliconoxide, polymers, and combinations thereof. In some embodiments, whichcan be combined with other embodiments described herein, the substrate101 includes a transparent material. Suitable examples may include anoxide, sulfide, phosphide, telluride or combinations thereof. In oneexample, the substrate 101 includes silicon (Si), silicon dioxide(SiO₂), germanium (Ge), silicon germanium (SiGe), sapphire, andhigh-index transparent materials such as high-refractive-index glass.

In some embodiments, which can be combined with other embodimentsdescribed herein, the device layer 114 includes, but is not limited to,one or more of silicon oxycarbide (SiOC), titanium dioxide (TiO₂),silicon dioxide (SiO₂), vanadium (IV) oxide (VOx), aluminum oxide(Al₂O₃), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tindioxide (SnO₂), zinc oxide (ZnO), tantalum pentoxide (Ta₂O₅), siliconnitride (Si₃N₄), zirconium dioxide (ZrO₂), niobium oxide (Nb₂O₅),cadmium stannate (Cd₂SnO₄), or silicon carbon-nitride (SiCN) containingmaterials. In some embodiments, which can be combined with otherembodiments described herein, the material of the device layer 114 mayhave a refractive index between about 1.5 and about 2.65. In otherembodiments, which can be combined with other embodiments describedherein, the material of the device layer 114 may have a refractive indexbetween about 3.5 and about 4.0.

FIG. 2 is a schematic, side view of an angled etch system 200. It is tobe understood that the angled etch system 200 described below is anexemplary angled etch system and other angled etch systems may be usedwith or modified to fabricate the optical devices 100 having blazeddevice structures 106 in accordance with the embodiments of thedisclosure.

The angled etch system 200 includes an ion beam chamber 202. A powersource 204, a first gas source 206, and a second gas source are coupledto the ion beam chamber 202. In one embodiment, which can be combinedwith other embodiments described herein, the power source 204 is a radiofrequency (RF) power source. The first gas source 206 is in fluidcommunication with the interior volume 205 of ion beam chamber 202. Thefirst gas source 206 is an inert gas source which supplies an inert gas,such as argon, hydrogen, or helium, to the ion beam chamber 202. Thesecond gas source 208 is in fluid communication with the interior volume205 of ion beam chamber 202. The second gas source 208 is a process gassource which supplies a process gas to the ion beam chamber 202. Theprocess gas includes, but is not limited to, one or more of a chlorinecontaining gas, a fluorine containing gas, a bromine containing gas, anoxygen containing gas, a silicon containing gas, nitrogen containinggas, hydrogen containing gas, or the like. In the embodiments of themethod 400 described herein, which can be combined with otherembodiments described herein, two or more process gases may be utilized.

A first process gas may have a substrate etch chemistry that isselective to a resist material. The etch selectivity of the firstprocess gas having the substrate etch chemistry provides for aselectivity of the substrate material to the resist material (describedbelow) of about 5:1 or greater. The etch selectivity of the firstprocess gas having the device material etch chemistry provides for aselectivity of the device material to a resist material of about 5:1 orgreater. In one embodiment, which can be combined with other embodimentsdescribed herein, the substrate etch chemistry includes a chlorinecontaining gas, a fluorine containing gas, or a combination thereof. Inanother embodiment, which can be combined with other embodimentsdescribed herein, the device material etch chemistry includes thechlorine containing gas, the fluorine containing gas, or the combinationthereof.

A second process gas may have a resist etch chemistry that is selectiveto the substrate material or device material. The etch selectivity ofthe second process gas having the resist etch chemistry provides for aselectivity of the resist material to the substrate material of about10:1 or greater or a selectivity of the resist material to the devicematerial of about 10:1 or greater. In one embodiment, which can becombined with other embodiments described herein, the resist etchchemistry includes oxygen gas (O₂) and carbon tetrafluoride (CF₄). Inanother embodiment, which can be combined with other embodimentsdescribed herein, the resist etch chemistry includes argon gas (Ar),nitrogen gas (N₂), and hydrogen gas (H₂). In yet another embodiment,which can be combined with other embodiments described herein, theresist etch chemistry includes nitrogen gas (N₂) and hydrogen gas (H₂).

In operation, a plasma is generated in the ion beam chamber 202 byapplying RF power via the power source 204 to the inert gas and theprocess gas provided to the interior volume 205 of ion beam chamber 202to generate a plasma. Ions of the plasma of the inert gas and theprocess gas are extracted through an aperture 210 of an extraction plate212 to generate an ion beam 216. The aperture 210 of the ion beamchamber 202 is operable to direct the ion beam 216 at an angle αrelative to a datum plane 218 oriented normal to the substrate 101(i.e., the surface normal s). The ion beam 216 includes, but is notlimited to, a spot beam, a ribbon beam, or a full substrate-size beam.The ion beam 216 generated includes one of the substrate etch chemistry,the device material etch chemistry, or the resist etch chemistrydependent on the process gas utilized.

The substrate 101 is retained on a platen 214 coupled to a firstactuator 219. The first actuator 219, which may be a linear actuator, arotary actuator, a stepper motor, or the like, is configured to move theplaten 214 in a scanning motion along a y-direction and/or az-direction. In one embodiment, which can be combined with otherembodiments described herein, the first actuator 219 is furtherconfigured to tilt the platen 214 such that the substrate 101 ispositioned at a tilt angle β relative to the x-axis of the ion beamchamber 202. The angle α and tilt angle β result in a beam angle ϑrelative to the datum plane 218 normal to the substrate 101. A secondactuator 220 may also be coupled to the platen 214 to rotate thesubstrate 101 about the x-axis of the platen 214.

FIG. 3 is a schematic, cross-sectional view of angled etch system 300.It is to be understood that the angled etch system 300 described belowis an exemplary angled etch system and other angled etch systems may beused with or modified to fabricate the optical devices 100 having blazeddevice structures 106 in accordance with the embodiments of thedisclosure.

The angled etch system 300 includes an electron beam chamber 302. Apower source 304, a first gas source 306, and a second gas source 308are coupled to the electron beam chamber 302. The first gas source 306and the second gas source 308 are in fluid communication with theinterior volume 305 of electron beam chamber 302. For example, the firstgas source 306 and the second gas source 308 may extend through theelectrode 322 or the electrode 322 may include a plurality of aperturesto function as a gas delivery showerhead. The first gas source 306 is aninert gas source which supplies the inert gas (as described above) tothe electron beam chamber 302. The second gas source 308 is a processgas source (as described above) which supplies a process gas to the ionbeam chamber 202. In the embodiments of the method 400 described herein,which can be combined with other embodiments described herein, two ormore process gases may be utilized. The two or more process gasesinclude the substrate etch chemistry, the device material etchchemistry, and the resist etch chemistry described herein.

The substrate 101 is retained on a platen 314 coupled to a firstactuator 321. The first actuator 321, which may be a linear actuator, arotary actuator, a stepper motor, or the like, is configured to raiseand lower the platen 314 within the electron beam chamber 302. A secondactuator 320 may also be coupled to the platen 314 to rotate thesubstrate 101 about a vertical axis of the platen 314. The platen 314includes an electrode 324 disposed therein. In one embodiment, theelectrode 324 is a chucking apparatus, such as an electrostatic chuck,for securing a substrate 101 thereto during processing of the substrate101. Power from the power source 304 may be utilized to bias theelectrode 324 to either chuck the substrate 101 to the electrode 324 orinfluence bombardment of electrons on the substrate 101.

In operation, a plasma is generated in the electron beam chamber 302 byvarious bulk and surface processes, for example, by inductive coupling.It is believed that ions generated by an inductively coupled plasma areinfluenced by an electric field that encourages bombardment of theelectrode 322 by the ions generated from the plasma of the inert gas andthe process gas. Other plasma generation processes, such as acapacitively coupled arrangement, hollow cathode arrangement, directcurrent electrode biasing, or electron beam plasma generation processesmay be utilized in accordance with the embodiments described herein.

Ion bombardment of the electrode 322 is believed to cause the electrode322 to emit secondary electrons. Energetic secondary electrons, whichhave a negative charge, are emitted from the electrode 322. As such, anelectron beam 316 is accelerated from the electrode 322 at beam angle ϑrelative to a datum plane 318 oriented normal to the substrate 101(i.e., the surface normal s). The electron beam 316 includes, but is notlimited to, a spot beam, a ribbon beam, or a full substrate-size beam.The electron beam 316 generated includes one of the substrate etchchemistry, the device material etch chemistry, or the resist etchchemistry dependent on the process gas utilized.

As described herein, the ion beam 216 generated from the angled etchsystem 200 (e.g., an ion beam etch system) and electron beam 316generated from the angled etch system 300 (e.g., an electron beam etchsystem) are collectively described as a beam 516 (as shown in FIGS.5A-5J) where the beam 516 is one of an ion beam or an electron beam. Inembodiments of the method 400, which can be combined with otherembodiments described, the beam 516 has one of the substrate etchchemistry, the device material etch chemistry, or the resist etchchemistry at operations of the method 400 described herein. In someembodiments, which may be combined with other embodiments describedherein, at least the substrate etch chemistry and resist etch chemistryare different. In other embodiments, which may be combined with otherembodiments described herein, at least the device material etchchemistry and resist etch chemistry are different. As described herein,the tunability of etch rates of the resist material 506 and one of adevice layer 114 or the substrate 101 and rotation of the substrate 101form the blazed optical device structures without multiple lithographicpatterning steps and angled etch steps.

FIG. 4 is a flow diagram of a method 400 for forming a plurality ofblazed device structures 106 of an optical device structure 100 as shownin FIGS. 5A-5E and 5F-5J. FIGS. 5A-5E are schematic, cross sectionalviews of a portion 501 of a substrate 101 during the method 400. FIGS.5F-5J are schematic, top views of the portion 501 of the substrate 101during the method 400.

To facilitate explanation, the method 400 will be described withreference to the angled etch system 200 of FIG. 2 and the angled etchsystem 300 of FIG. 3. However, it is to be noted that angled etchsystems other than the angled etch systems 200, 300 may be utilized inconjunction with method 400. In one embodiment, which can be combinedwith other embodiments described herein, the portion 501 may correspondto a portion or a whole surface of the substrate 101 of a flat opticaldevice to have the plurality of blazed device structures 106 formedthereon. In another embodiment, which can be combined with otherembodiments described herein, the portion 501 may correspond to aportion or a whole surface of the substrate 101 of a waveguide combinerto have the plurality of blazed device structures 106 formed thereon.The portion 501 may correspond to one or more gratings 104. While FIGS.5A-5E and FIGS. 5F-5J depict etching the substrate 101 such that theblazed device structures 106 are disposed in the substrate, a devicelayer 114 (as described above) may be disposed on the surface 103 suchthat the blazed device structures 106 are disposed in the device layer114.

At operation 401, as shown in FIGS. 5A and 5F, a substrate 101 ispositioned at a first rotation angle ϕ₁ as defined by datum line 502, asshown in FIG. 5F. In one embodiment, which may be combined with otherembodiments described herein, the first rotation angle ϕ₁ is 0° definedby datum line 502. The substrate 101 or the device layer 114 (not shown)includes a patterned resist 504 disposed thereon. The pattern resist 504includes a resist material 506 that is patterned into a plurality ofresist structures 508 disposed over a surface 103 of substrate 101. Theresist material 506 of the patterned resist 504 is selected based on thesubstrate etch chemistry (in embodiments in which the substrate 101 isetched to form the blazed device structures 106) or the device materialetch chemistry (in embodiments in which the device layer 114 is etchedto form the blazed device structures 106). In one embodiment, the resistmaterial 506 is a photosensitive material such that the patterned resist504 may be patterned by a lithography process, such as photolithographyor digital lithography, or by laser ablation process to form theplurality of resist structures 508. In one embodiment, the resistmaterial 506 is an imprintable material that the patterned resist 504may be patterned by a nanoimprint process to form the plurality ofresist structures 508. In another embodiment, which may be combined withother embodiments described herein, the resist material 506 is ahardmask material and the patterned resist 504 is a patterned via one ormore etch processes to form the plurality of resist structures 508. Inyet another embodiment, which may be combined with other embodimentsdescribed herein, the patterned resist 504 is an optical planarizationlayer.

Each resist structure 508 includes a bottom surface 509, a firstsidewall 510, a second sidewall 512, and a top surface 514. Each resiststructure 508 has a height 515 from the bottom surface 509 to the topsurface 514. Each resist structure 508 has a width 522 from the firstsidewall 510 to the second sidewall 512 of the resist structure 508. Aplurality of gaps 518 are defined by adjacent resist structures 508.Each of the gaps 518 has a linewidth 520 between the first sidewall 510and the second sidewall 512 of adjacent resist structures 508. Theheight 515, the linewidth 520, and the width 522 are selected to tunethe number of steps 110 of blazed surface 108 and the linewidth d of theplurality of blazed device structures 106. For example, increasing theheight 515 increases the number of repeated intervals of etching thesubstrate 101 (or device layer 114) and the resist structure 508 suchthat the number of steps 110 is increased.

At operation 402, the substrate 101 is exposed to the beam 516 at thebeam angle ϑ relative to the surface normal of the substrate 101. In oneembodiment, which can be combined with other embodiments describedherein, the beam angle ϑ is about 10 degrees to about 80 degreesrelative to the surface normal of the substrate 101. The beam 516 hasthe substrate etch chemistry or device etch chemistry that is selectiveto the resist material 506, i.e., exposed portions 517 of the substrate101 or exposed portions of the device layer 114 (not shown) are removedat a higher rate than the resist material 506. After the beam 516 etchesthe exposed portions of the substrate 101, at operation 402 (as shown inFIG. 5B) the depth h of the exposed portions 517 corresponding to theblazed device structures 106 is formed.

At operation 403, substrate 101 is rotated to a second rotation angle ϕ₂defined by datum line 502, as shown in FIG. 5H. In one embodiment, whichcan be combined with other embodiments described herein, the platen 214,314 retaining substrate 101 is rotated to a second rotation angle ϕ₂. Inanother embodiment, which can be combined with other embodimentsdescribed herein, the second rotation angle ϕ₂ corresponds to 90°relative to datum line 502. The rotating of the substrate 101 is notlimited to a rotation angle ϕ corresponding to 90° but may correspond toany predetermined angle ϕ. The rotation enables the beam 516 to contactresist structures 508 due to a shadowing effect. In one embodiment,which can be combined with other embodiments described herein, the beam516 will remain at a beam angle ϑ relative to a datum plane 218, 318oriented normal to the substrate 101 (i.e., the surface normal s)throughout method 400. The constant beam angle allows for the throughputto increase because there will not be a need to reconfigure the beamangle ϑ. In one embodiment, which can be combined with other embodimentsdescribed herein, the method 400 described herein uses only one angledetch system 200, 300 and requires the resist material 506 to only bepatterned once to provide for high volume production capability.

At operation 404, the resist structures are exposed to the beam 516 atthe beam angle ϑ. The beam 516 etches one of either the first sidewall510 or the second sidewall 512, corresponding to which sidewall 510, 512is exposed to the beam 516. In the embodiment which can be combined withother embodiments described herein, the first sidewall 510 is exposed tothe beam 516. The beam 516 has a chemistry corresponding to the resistetch chemistry so that the ions or electrons will only substantiallyetch the resist structures 508 during the resist etch process. Theresist etch chemistry is selective to the substrate 101 or device layer114, i.e., the resist structures 508 are removed at a higher rate thanthe device layer 114 or substrate 101. After the beam 516 etches theresist structures 508, the width 522 of resist structure 508 decreasesrelative to the width shown in FIGS. 5A and 5B. The linewidth 520between the first sidewall and the second sidewall increases relative tothe linewidth shown in FIGS. 5A and 5B.

As shown in FIG. 5C, a first step of the plurality of steps 110 isformed. The plurality of steps 110 forms the blazed surface 108 shown inFIGS. 1B and 1C. The blaze angle γ is the angle between the blazedsurface 108 and the surface parallel p of the substrate 101. The blazeangle γ may be achieved by increasing or decreasing the etch rate ofbeam 516. The adjustments of blaze angle γ may be accomplished byetching at different rates such that depth h, linewidth 520 and width522 are at predetermined values corresponding to a different number ofsteps 110 formed on blazed surface 108. Thus, the blaze angle γ may beadjusted and the blazed device structures 106, such as the blazed devicestructures 106 of a grating 104, may modulate light propagating throughthe optical device 100 as desired.

At operation 405, operations 401-404 are repeated until a predeterminednumber of steps 110 (as shown in FIGS. 1B and 1C) are formed on opticaldevice 100. In one embodiment, which can be combined with otherembodiments described herein, the substrate 101 is rotated to the firstrotation angle ϕ₁ and substrate 101 or device layer 114 are etched withthe beam 516 until the resist structures 508 are removed or thelinewidth 520 of the gaps 518 has a predetermined linewidth. As shown inFIG. 5I, the platen 214, 314 with substrate 101 positioned thereon isrotated to a first rotation angle ϕ₁. As shown in FIG. 5D, the depth hof the exposed portions 517 corresponding to the blazed devicestructures 106 increases relative to the depth h shown in FIGS. 5A-5C.As shown in FIG. 5J, the platen 214, 314 with substrate 101 positionedthereon is rotated to a second rotation angle ϕ₂ defined by datum line502. After the beam 516 etches the resist structures 508, the width 522of resist structure 508 decreases relative to the width shown in FIGS.5A-5D. The linewidth 520 between the first sidewall 510 and the secondsidewall 512 increases relative to the linewidth 520 shown in FIGS.5A-5D. At optional operation 406, residual resist material 506 disposedon the device layer 114 or substrate 101 is removed. While only fourresist structures 508 and three gaps 518 are illustrated, the entirepatterned resist 504 may be etched such that the desired number ofblazed device structures 106 are formed depending on the predetermineddesign for the optical device 100.

In summation, methods of forming optical device structures are describedherein. The methods utilize rotation of a substrate, to have the blazedoptical device structures formed thereon, and tunability of etch ratesof a patterned resist disposed over the substrate and one of a devicelayer or the substrate to form the blazed optical device structureswithout multiple lithographic patterning steps and angled etch steps.The constant beam angle allows for the throughput to increase becausethere will not be a need reconfigure the beam angle ϑ. Only one angledetch system may be used and the resist material would only need to bepatterned once to provide for high volume production capability.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method, comprising: positioning a substrate ata first rotation angle ϕ₁ in a path of a beam, the beam configured to beprojected to a surface of the substrate at a beam angle ϑ relative to asurface normal of the substrate, the substrate having a patterned resistformed thereover, the patterned resist comprising: two or more resiststructures, each of the resist structures having a width; and one ormore gaps, each of the gaps defined by adjacent resist structures andhaving a linewidth defined by the adjacent resist structures; etchingthe substrate positioned at the first rotation angle ϕ₁ with the beam;rotating the substrate to a second rotation angle ϕ₂ and etchingsidewalls of the resist structures oriented toward the beam such thatthe width of the resist structures decreases and the linewidth of thegaps increases; rotating the substrate to the first rotation angle ϕ₁and etching the substrate at the first rotation angle ϕ₁ with the beam;and forming two or more optical device structures in the substrate, theforming the optical device structures comprising: repeating the rotatingthe substrate to the second rotation angle ϕ₂ and the etching sidewallsof the resist structures with the beam, and the rotating the substrateto the first rotation angle ϕ₂ and the etching the substrate with thebeam until the resist structures are removed or the linewidth of thegaps has a predetermined linewidth.
 2. The method of claim 1, whereinthe etching the substrate at the first rotation angle ϕ₁ comprisesgenerating the beam with a substrate etch chemistry that etches thesubstrate at a greater rate than the patterned resist.
 3. The method ofclaim 1, wherein the etching the sidewalls of the resist structurescomprises generating the beam with a resist etch chemistry that etchesthe patterned resist at a greater rate than the substrate.
 4. The methodof claim 1, wherein the first rotation angle ϕ₁ is 0°.
 5. The method ofclaim 1, wherein the second rotation angle ϕ₂ is 90°.
 6. The method ofclaim 1, wherein the beam angle ϑ is about 10° to about 80°.
 7. Themethod of claim 1, wherein the resist structures includesphotosensitive, imprintable, optical planarization, or hardmaskmaterials.
 8. The method of claim 1, wherein the optical devicestructures include at least 32 steps.
 9. The method of claim 1, whereinthe beam is a ribbon beam, a spot beam, or a full substrate-size beam.10. The method of claim 1, wherein the beam is an ion beam or anelectron beam.
 11. A method, comprising: positioning a substrate at afirst rotation angle ϕ₁ in a path of a beam, the beam configured to beprojected to a surface of the substrate at a beam angle ϑ relative to asurface normal of the substrate, the substrate having a device layerdisposed thereon and a patterned resist formed on the device layer, thepatterned resist comprising: two or more resist structures, each of theresist structures having a width; and one or more gaps, each of the gapsdefined by adjacent resist structures and having a linewidth defined bythe adjacent resist structures; etching the device layer with thesubstrate positioned at the first rotation angle ϕ₁ with the beam;rotating the substrate to a second rotation angle ϕ₂ and etchingsidewalls of the resist structures oriented toward the beam such thatthe width of the resist structures decreases and the linewidth of thegaps increases; rotating the substrate to the first rotation angle ϕ₁and etching the device layer at the first rotation angle ϕ₁ with thebeam; and forming two or more optical device structures in the devicelayer, the forming the optical device structures comprising: repeatingthe rotating the substrate to the second rotation angle ϕ₂ and theetching sidewalls of the resist structures with the beam and rotatingthe substrate to the first rotation angle ϕ₁ and the etching the devicelayer with the beam until the resist structures are removed or thelinewidth of the gaps has a predetermined linewidth.
 12. The method ofclaim 11, wherein the etching the device layer comprises generating thebeam with a device material etch chemistry that etches the device layerat a greater rate than the patterned resist.
 13. The method of claim 12,wherein an etch selectivity of the device material to the patternedresist is about 5:1 or greater.
 14. The method of claim 11, wherein theetching the sidewalls of the resist structures comprises generating thebeam with a resist etch chemistry that etches the patterned resist at agreater rate than the device layer.
 15. The method of claim 14, whereinan etch selectivity of the patterned resist to the device layer is about10:1 or greater.
 16. The method of claim 11, wherein the first rotationangle ϕ₁ is 0° and the second rotation angle ϕ₂ is 90°.
 17. The methodof claim 11, wherein the beam is a ribbon beam, a spot beam, or a fullsubstrate-size beam.
 18. The method of claim 11, wherein the opticaldevice structures include at least 32 steps.
 19. The method of claim 11,wherein the device layer includes one or more of silicon oxycarbide(SiOC), titanium dioxide (TiO₂), silicon dioxide (SiO₂), vanadium (IV)oxide (VOx), aluminum oxide (Al₂O₃), aluminum-doped zinc oxide (AZO),indium tin oxide (ITO), tin dioxide (SnO₂), zinc oxide (ZnO), tantalumpentoxide (Ta₂O₅), silicon nitride (Si₃N₄), zirconium dioxide (ZrO₂),niobium oxide (Nb₂O₅), cadmium stannate (Cd₂SnO₄), or siliconcarbon-nitride (SiCN) containing materials.
 20. A method, comprising:positioning a substrate at a first rotation angle ϕ₁ in a path of abeam, the beam configured to be projected to a surface of the substrateat a beam angle ϑ relative to a surface normal of the substrate, thesubstrate having a patterned resist formed thereover, the patternedresist comprising: two or more resist structures, each of the resiststructures having a width; and one or more gaps, each of the gapsdefined by adjacent resist structures and having a linewidth defined bythe adjacent resist structures, wherein: the substrate is etched by thebeam generated by a substrate etch chemistry; and the resist structuresare etched by the beam generated by a resist etch chemistry differentthan the substrate etch chemistry; etching the substrate positioned atthe first rotation angle ϕ₁ with the beam generated by the substrateetch chemistry; rotating the substrate to a second rotation angle ϕ₂ andetching sidewalls of the resist structures with the beam at the beamangle ϑ, the beam generated by the resist etch chemistry etchingsidewalls of resist structures oriented toward the beam such that thewidth of the resist structures decreases and the linewidth of the gapsincreases; rotating the substrate to the first rotation angle ϕ₁ andetching the substrate at the first rotation angle ϕ₁ with the beamgenerated by the substrate etch chemistry; and forming two or moreoptical device structures in the substrate, the forming the opticaldevice structures comprising: repeating the rotating the substrate tothe second rotation angle ϕ₂ and the etching sidewalls of the resiststructures with the beam generated by the resist etch chemistry, androtating the substrate to the first rotation angle ϕ₁ and the etchingthe substrate with the beam generated by the substrate etch chemistryuntil the resist structures are removed or the linewidth of the gaps hasa predetermined linewidth.